1. Field of the Invention
The present disclosure relates to a light source device; in particular, to wide band fiber light source devices employing a coolerless pump laser for harsh environment applications such as over temperature and under radiation.
2. Description of Related Art
Pump lasers are common devices in the fields of optical sensing and communications. A pump laser produces a high efficiency, single color and concentrated light beam. Pump lasers are easily affected by temperature, leading to the mean wavelength and the peak power value of the light beam to move with temperature. In order to decrease the effect of temperature on the mean wavelength and the peak power value of the light beam produced by the pump laser, common solution is to employ a thermoelectric cooler (TEC) to stabilize the pump laser temperature. However, TEC with its associated controlled circuit consumes additional power which is not desirable, especially for space applications.
Broadband ASE (amplified spontaneous emission) fiber light source consisting of a pump laser is a key element of a fiber optic gyroscope or fiber sensors. A fiber optic gyroscope functions based on light beams passing through hundreds to thousands of meters of optic fiber coils and interference resulting therefrom. Two light beams respectively enter two ends of an optic fiber sensing loop at the same time. Due to Sagnac effect, under a condition of clockwise and counterclockwise rotations, the path of one light beam is shorter than that of the other light beam such that phase shifts occur between the two counter-propagating light beams. A synchronous detection can sense the phase shift, thereby obtaining the magnitude and direction of angular rotation. The scale factor of the fiber optic gyroscope is however proportional to the mean wavelength of the wide band ASE light source pumped by the pump laser which is sensitive to temperature if no TEC is used. Therefore the goal is to achieve consistency of the mean wavelength of the broadband ASE light source device when a coolerless pump laser is used. Namely, the mean wavelength and the power value of the broadband ASE light beam pumped by the coolerless pump laser cannot be easily affected by temperature or radiation if the coolerless pump laser is intended for space applications.
Through devoted researches combined with theoretical modelings, the present inventors had demonstrated the present disclosure which employs a coolerless pump laser and achieve mean wavelength and power stability of a broadband ASE fiber light source over harsh temperature and radiation environment.